Cancer is the second leading cause of death in the United States, exceeded only by heart disease. (Cancer Facts and Figures 2004, American Cancer Society, Inc.). Despite recent advances in cancer diagnosis and treatment, surgery and radiotherapy may be curative if a cancer is found early, but current drug therapies for metastatic disease are mostly palliative and seldom offer a long-term cure. Even with new chemotherapies entering the market, the need continues for new drugs effective in monotherapy or in combination with existing agents as first line therapy, and as second and third line therapies in treatment of resistant tumors.
Cancer cells are by definition heterogeneous. For example, within a single tissue or cell type, multiple mutational “mechanisms” may lead to the development of cancer. As such, heterogeneity frequently exists between cancer cells taken from tumors of the same tissue and same type that have originated in different individuals. Frequently observed mutational “mechanisms” associated with some cancers may differ between one tissue type and another (e.g., frequently observed mutational “mechanisms” leading to colon cancer may differ from frequently observed “mechanisms” leading to leukemias). It is therefore often difficult to predict whether a particular cancer will respond to a particular chemotherapeutic agent (Cancer Medicine, 5th edition, Bast et al., B. C. Decker Inc., Hamilton, Ontario).
Components of cellular signal transduction pathways that regulate the growth and differentiation of normal cells can, when dysregulated, lead to the development of cellular proliferative disorders and cancer. Mutations in cellular signaling proteins may cause such proteins to become expressed or activated at inappropriate levels or at inappropriate times during the cell cycle, which in turn may lead to uncontrolled cellular growth or changes in cell-cell attachment properties. For example, dysregulation of receptor tyrosine kinases by mutation, gene rearrangement, gene amplification, and overexpression of both receptor and ligand has been implicated in the development and progression of human cancers.
Calcium-calmodulin-dependent protein kinase II (CaMKII) is an important regulator of neuronal and behavioral plasticity. CaMKII is encoded by four genes in mammals: α, β, γ, and δ. The CaMKII isozymes are not uniformly expressed in time and space; α and β are found primarily in nervous tissue with β expression initiating during embryonic development and a postnatally. The isozyme α is the primary CaMKII in the forebrain, whereas β is the primary cerebellar isozyme. β is also found in glia. The γ and δ isozymes are found at low levels in all tissues with enrichment of various splice forms in particular non-neuronal tissues. Each gene encodes a protein that has an N-terminal serine-threonine kinase domain, followed by a regulatory region with an autoinhibitory sequence and a calmodulin-(CaM)-binding site. The C-terminus is usually called the association domain and is responsible for assembly of subunits into large (estimates range from 8 to 14 subunit) multimers.
CaMKII acts as an autophosphorylation-regulated molecular switch. Binding of Ca2+-CaM to the regulatory domain of the kinase activates the kinase by releasing the catalytic domain from inhibition by autoregulatory sequences proximal to the CaM binding site. This allows the kinase to both phosphorylate itself and its substrates. Autophosphorylation renders the kinase Ca2+/CaM-independent, although the activity of this form of the kinase is less than the Ca2+-CaM bound form. The autophosphorylation and isozyme-specific structural properties of CaMKII provide important mechanisms for regulating its localization.
It has recently been shown that prostate cancer cells express β, γ, and δ CaMKII genes, and the expression of these genes is under the control of androgen receptor activity. Androgen receptor is the main factor required for prostate cancer cells survival and studies have shown a cross-talk between this receptor and CaMKII-mediated pathways. Overexpression of CaMKII increases secretion of prostate specific antigen and promotes cell growth and recent studies demonstrate that CaMKII is an important player in prostate cancer cells ability to escape apoptosis under androgen ablation and facilitate the progression of prostate cancer cells to an androgen independent state
Cyclin-dependent kinases (CDK) belong to a group of serine/threonine kinases originally discovered as being involved in the regulation of the cell cycle and have been long considered essential for normal proliferation, development and homeostasis. CDKs are also involved in the regulation of transcription and mRNA processing. To date, there are various isoforms of CDK from CDK1-CDK11. A cyclin-dependent kinase is activated by association with a cyclin, forming a cyclin-dependent kinase complex.
The importance of the Cdk-cyclin complexes in cell proliferation is underscored by the finding that deregulation of the Cdk activity is found in virtually the whole spectrum of human tumors. Thus, the regulation of CDK activity is essential in the treatment of various proliferation disorders such as cancer. Tumor-associated cell cycle defects are often mediated by alterations in CKD activity. Misregulated CDKs induce unscheduled proliferation, as well as, genomic and chromosomal instability. CDK inhibitors, such as p27 (also known as KIP1), have been shown to regulate cell proliferation, cell motility and apoptosis.
Accordingly, new compounds and methods for modulating CaMKII and CDK genes and treating proliferation disorders, including cancer, are needed. The present invention addresses these needs.